A commonly known form of fuel tank for a motorcycle includes a closed tank which is disposed above a frame of the motorcycle and which has a fuel inlet in an upwardly presented surface thereof, the fuel inlet being of tubular form and having cam surfaces at the upper end thereof for interlocking engagement with a removable closure cap.
Owing to the somewhat shallow depth of such a fuel tank as compared with the length of the fuel inlet of an automobile, a fuel nozzle of the automatic cut-off type cannot be used in its intended manner, and, as a consequence, manually controlled filling of the fuel tank is necessitated, with the necessity of observing the level of the fuel as it rises in the tank in order to avoid over filling of the tank and spillage of the fuel.
While this does not pose a particular problem in those instances where the engine is designed to operate on a fuel such as conventional leaded gasoline, in which event the inlet can be made conveniently large enough to permit viewing of the interior of the tank at the time the fuel nozzle is disposed within the inlet, it poses acute problems in those instances where the engine is designed to operate on a fuel such as unleaded gasoline, in which event the inlet must be dimensioned for it to accept only the fuel nozzle employed for dispensing unleaded gasoline, and, for it to be too small in diameter for it to accept the larger diameter nozzle employed for dispensing leaded gasoline.
As a consequence of the requirement for the inlet to reject the said larger diameter nozzle, the inlet must be made of smaller diameter than the diameter of said larger nozzle, which in turn severely limits the area available for viewing of the interior of the tank at the time the appropriate nozzle is disposed in the inlet for dispensing unloaded gasoline.